The invention relates to multiphase personal washing bars having an artisan-crafted appearance, and, more particularly, to high throughput extrusion processes for making such bars which are suitable for everyday use. The bars made by the process comprise a discontinuous phase having its longest dimension between about 3 and about 75 mm that is dispersed in a continuous phase containing a cleansing base. By ensuring the hardness of the continuous phase is within certain limits, and that the ratio of the hardness of the two phases measured at specific temperatures is greater than a critical value, it is possible to extrude the composition at high speed (e.g., at least about 200 bars/minute, preferably in excess of 300 bars/minute) while maintaining spatially distinct regions at the surface of the bar as measured by a visual discrimination panel test. Plasticizing and hardening agents that can be used to alter the rheology of the phases in order to meet these constraints are described.
Multicolor or multiphase soaps have been described by various terms that include variegated, marbled, striated, and striped. Prior art has mainly focused on routes to reproducibly achieve spatial variation in dye or pigment concentration as the primary means of generating bars that appear as comprising multiple phases.
Key technical problems that were recognized early in the commercial exploitation of such bars were: efficient manufacture with consistent patterns; distinctive contrast between the different colors especially at the bar surface; and the elimination of cracking, fissuring, and color migration (xe2x80x9cbleedingxe2x80x9d) during storage and use. Commercial processes and machines are now available to produce multicolor soaps that have highly consistent appearance.
The multicolor nature of the prior art bars gives the impression that the bars comprise distinct phases that have different ingredients or function. However, the vast majority of multicolored bars disclosed in the art and sold in the mass market have virtually homogeneous composition and few different properties apart from gradients in coloring agents. Incomplete mixing during manufacture of the bar essentially produces these dye gradients.
With the resurgence in the specialty soap market, consumers are being offered multicolor/multiphase bars that have a much more hand crafted (i.e., xe2x80x9cartisan craftedxe2x80x9d) xe2x80x9cone-of a kindxe2x80x9d appearance. Technically such bars have at least the following three characteristics that contribute to their distinctive appearance: i) The sharpness of the boundary between the phases; ii) an easily recognizable difference in optical texture and/or pattern that goes beyond color, and iii) a certain degree of bar to bar non-uniformity. Differences in optical texture and pattern are especially important to convey a collection of sensory expectations associated with that phase. Examples include translucency, shine, and sharp edges to convey a gel; circular dark patterns or repeating textures to convey fruit, etc.
Artisan soaps are predominantly made by cast melt processesxe2x80x94either single casting or sequential multiple casts. Because these cast melt processes are slow and labor intensive, multiphase artisan soaps are relatively expensive and confined to upscale specialty shops and outlets. Furthermore, cast melt soaps are known to have high wear rates and mushing characteristics that make them less preferred for everyday use.
One objective of the present invention is a multiphase bar soap that has an artisan-crafted appearance yet can be produced by a conventional high speed (e.g., at least about 200 bars/minute) extrusion process with only minor equipment modifications and requires minimum (preferably no), trimming.
A second objective is an extruded multiphase soap wherein the phases have sharp boundaries, recognizable differences in optical texture and pattern, and different composition.
A third objective is a multiphase soap having an artisan-crafted appearance that has in-use properties and unit-cost that will make it suitable for the mass market.
A still further objective is the production of extruded multiphase soap bars that will have adequate bar to bar variability to convey distinctiveness.
Another specific objective of the subject invention is a process for making such bars.
As will be shown, these and other objectives can be met by following the teachings of the present invention.
U.S. Pat. No. 3,673,294 to Matthaei et al, teach a process to form multicolored bars by extruding a mixture of two noodles which are required to have the same viscosity and essentially the same hardness (penetration value).
U.S. Pat. No. 3,940,220 to D""Arcangeli teaches the extrusion of a mixture of two noodles in which it is required that the discontinuous phase be softer (lower penetration value) than the main soap. In the bars made by the process of subject invention, the discontinuous phase is harder.
U.S. Pat. No. 3,993,722, to Borcher et al and U.S. Pat. No. 4,092,388 to Lewis teach processes of combining different colored noodles to formed marbled soap. The two noodles have essentially the same composition (e.g., hardness) apart from colorant and the two different color noodles have essentially the same temperature at the time of extrusion.
U.S. Pat. No. 4,310,479 to Ooms et al teaches a process for combining a minor amount of opaque noodles with transparent noodles to form a transparent marbled bar. The noodles should differ in water content by no more than 3% and are at the same temperature during extrusion. Accordingly, hardness of the noodles and bar is about the same.
U.S. Pat. No. 6,390,797 to Meyers teaches a process for making marbleized or speckled soap by addition of a second stream of colored soap pellets into the interior of the final stage plodder at a specific point. No mention is made about the hardness of the two phases or their required properties or of processes of making bars of the invention.
U.S. Pat. No. 3,884,605 to Grelon teaches an apparatus for making striated soap made by coextrusion where it is desirable that the two soaps have identical material properties, e.g., hardness, apart from color.
U.S. Pat. No. 6,383,999 to Coyle et al teach a coextruded multiphase bar in which the phases differ in the level of emollient but must have similar flow properties under extrusion process conditions.
U.S. Pat. No. 5,935,917 to Farrell et al, U.S. Pat. No. 5,972,859 to Farrell et al and U.S. Pat. No. 5,981,464 to He et al teach bar compositions comprised of surfactant chips mixed with a second chip comprised predominantly of polyether and containing an emulsified benefit agent. The polyether chips are friable by design so that they disperse when mixed with the soap chips.
None of these patents teach that the discontinuous phase of a multiphase bar should be at least twice as hard as the soap mass that will become the continuous phase of the bar when these two phases first come into contact prior to the final extrusion. For example many patents teach the combining of different color noodles in the vacuum chamber of a two state refiner-plodder. However none of these patents teach that one noodle should be at leas twice as hard as the other colored noodle when these noodles are initially combined.
Further the art does not teach appropriate plasticizers and hardening agents that enable these rheological requirements to be met. In fact the large majority of the prior art emphasize engineering approaches (apparatus and different processes) to overcome problems in making acceptable multicolor soaps using soaps of uniform composition apart from coloring agents.
The subject invention describes multiphase personal washing bars that have a artisan-crafted appearance that can be made in a high speed extrusion process by ensuring that the hardness of the discontinuous phase is sufficiently greater than the continuous phase so that it does not excessively deform during extrusion.
More specifically, the invention comprises:
a) a continuous solid phase covering about 65% to 99% by wt final bar composition and comprising 25-90% of the continuous phase composition of a surfactant base suitable for cleansing the skin,
b) a discontinuous phase (present as one or more xe2x80x9cdomainsxe2x80x9d of discontinuous phase within the continuous phase) comprising about 1 to about 35% of final bar composition and that comprises a water soluble or water dispersible solid matrix comprising at least 1 wt % surfactant wherein said discontinuous phase has its longest dimension between about 3 and about 75 mm,
wherein the hardness of the continuous phase is in the range of 1.9 to 2.5 bar. (1 bar equals 100,000 Pascals) when measured at a temperature between 33 and 50xc2x0 C., preferably 30 and 42xc2x0 C. wherein the ratio, xcex, defined as the hardness of the discontinuous phase measured at a temperature of 25xc2x0 C. divided by the hardness of the continuous phase measured at a temperature of 33xc2x0 C. is greater than 2.0; and wherein said hardness values are measured by the Cylinder Impaction Test;
wherein the discontinuous phase comprises 1 to about 25 wt % of the bar, and
wherein the bar has a descriptive visual grading score of at least 3.0 when measured by Visual Discrimination Panel Test.
The temperature noted above approximately reflects the thermal conditions of each phase during the time of extrusion and, without wishing to be bound by theory, when these conditions are met, the discontinuous phase is believed to not deform excessively, under shear, and therefore, is believed to allow formation of the artisan-type bars.
A second embodiment of the invention, comprises a process for making a bars having an artisan crafted appearance by extrusion wherein said process comprises:
1) adding to noodles comprising the continuous phase of a toilet bar mass that is at a temperature about 33 to 50xc2x0 C., a second solid mass that is in the form of discrete particles having at least one dimension greater that 3 mm to form a mixture, wherein at the time of addition, the hardness values measured by the Cylinder Impaction Test;
2) extruding the mixture so formed in step 1) to form an extruded composite mass comprising a continuous toilet bar mass and a disontinuous phase of the second solid mass;
3) cutting and forming the extruded mass into a bar
wherein the discontinuous phases 1 to about 25 wt % of the bar, and wherein the bar has a visual grading score of at least 3.0 when measured by Visual Discrimation Panel Test.